1. Technical Field
The present invention relates to an imaging sensor and an imaging device.
2. Related Art
Conventionally, an imaging sensor including a column-parallel A/D converter (simply referred to as an ADC) has been known. Also, a block-parallel ADC has been proposed for an imaging sensor in which signal processing chip is stacked (please see for example Non-Patent Document 1).
Non-Patent Document 1: “A Very Low Area ADC for 3-D Stacked CMOS Image Processing System” K. Kiyoyama et al., IEEE 3DIC 2012.
The column-parallel ADC is provided for each pixel column, and each reads out a pixel signal of each pixel in a selected row in parallel. However, because a conventional column-parallel ADC is formed on the same plane with an effective pixel area (for example, above and below in the column direction of the effective pixel area), the area of the imaging sensor increases. Also, when a plurality of rows are subjected to parallel/high speed processing, interconnections have to be routed in the effective pixel area. Also, when the plurality of rows are subjected to parallel/high speed processing, the size of an ADC becomes large, and the area of the imaging sensor further increases.
On the other hand, a block-parallel ADC is provided for each block of effective pixels (for example, for each block of ten pixels×ten pixels). However, in order to read out each pixel in a block with a single ADC, devices such as to use a complicated control line or to arrange, on an imaging chip side, a transistor for control become necessary. Also, an ADC for each block respectively operates independently. For this reason, an ADC generates heat independently, and a signal processing chip may generate heat locally. Local heat generation in a signal processing chip is transmitted to a stacked imaging chip, and can influence operation of the imaging chip.